A three-dimensional model simulation is a technique for setting virtual three-dimensional simulation space in a computer, setting the shape of a three-dimensional object model in the three-dimensional simulation space, and simulating an actual physical phenomenon of the three-dimensional object model by computation. In the response of a three-dimensional model simulation, a technique such as three-dimensional CAD, structure analysis simulation, computer graphics, or virtual reality is used.
In a three-dimensional model simulation, a deformable sheet object model with flexibility (hereinafter referred to as a sheet flexible object) such as a piece of paper, a film, a flexible printed circuit board, a flat cable, or a piece of electronic paper is sometimes used. For example, when a simulation target apparatus model (hereinafter referred to as a target apparatus) set in three-dimensional simulation space is designed, the target apparatus may include a flexible printed circuit board that is one of sheet flexible objects. For example, when a target apparatus is a flip phone, a flexible printed circuit board may be disposed at a hinge portion of the flip phone. When the flip phone is folded, the flexible printed circuit board becomes deformed in accordance with the folding operation. In a three-dimensional model simulation, when the flip phone is folded, it is possible to determine whether the shape and position of the flexible printed circuit board at the hinge portion of the flip phone are acceptable or to check the interference of the flexible printed circuit board with another object in the flip phone by computation.
Examples of a technique for simulating the shape of a deformable sheet flexible object include a mass-spring method of mesh-dividing a sheet flexible object into triangle or square polygon elements, setting mass points at vertices of the polygon elements, and connecting the mass points with, for example, spring elements. The shape of the sheet flexible object is specified by calculating a position where the mass points and the spring elements are dynamically stable.
When a sheet flexible object interferes with another object in a target apparatus, the sheet flexible object is deformed along the surface of the object. This deformation is hereinafter referred to as a “profiling deformation”. When the simulation of a profiling deformation is performed using a mass-spring method, a sheet flexible object is deformed along the surface of another object so as not to be pushed into the object. At that time, the sheet flexible object is moved so that there is no mass point of the sheet flexible object in another object. It is generally desirable to obtain an accurate computation result in a three-dimensional model simulation. Accordingly, in order to allow a sheet flexible object to freely deform, the mass-spring model of the sheet flexible object is finely divided into polygon elements.
However, the amount of computation performed when a sheet flexible object interfering with another object is deformed is proportional to the number of mass points. When a sheet flexible object locally interferes with another object, for example, only a part of the sheet flexible object curves outward. That is, the local deformation of the sheet flexible object easily occurs. Such a local deformation is unnatural, because it can be assumed that a flexible object such as a flexible printed circuit board cannot be stretched. Thus, in the related art disclosed in, for example, Japanese Laid-open Patent Publication Nos. 2002-275721, 2008-234039, and 2002-231074, the number of checks for interference between a sheet flexible object and another object is increased, and an unnatural deformation occurs at a point of interference between the sheet flexible object and another object.